Rollup merge of #110210 - nnethercote:DescriptionCtx-cleanups, r=davidtwco

`DescriptionCtx` cleanups

Best reviewed one commit at a time.

r? `@davidtwco`

Author: matthiaskrgr

compiler/rustc_infer/messages.ftl

@@ -163,7 +163,6 @@ infer_region_explanation = {$pref_kind ->
     [as_defined] the lifetime `{$desc_arg}` as defined here
     [as_defined_anon] the anonymous lifetime as defined here
     [defined_here] the anonymous lifetime defined here
-    [anon_num_here] the anonymous lifetime #{$desc_num_arg} defined here
     [defined_here_reg] the lifetime `{$desc_arg}` as defined here
 }{$suff_kind ->
     *[should_not_happen] [{$suff_kind}]

compiler/rustc_infer/src/errors/note_and_explain.rs

@@ -4,12 +4,10 @@ use rustc_errors::{self, AddToDiagnostic, Diagnostic, IntoDiagnosticArg, Subdiag
 use rustc_middle::ty::{self, TyCtxt};
 use rustc_span::{symbol::kw, Span};
 
-#[derive(Default)]
 struct DescriptionCtx<'a> {
     span: Option<Span>,
     kind: &'a str,
     arg: String,
-    num_arg: u32,
 }
 
 impl<'a> DescriptionCtx<'a> {
@@ -18,102 +16,74 @@ impl<'a> DescriptionCtx<'a> {
         region: ty::Region<'tcx>,
         alt_span: Option<Span>,
     ) -> Option<Self> {
-        let mut me = DescriptionCtx::default();
-        me.span = alt_span;
-        match *region {
-            ty::ReEarlyBound(_) | ty::ReFree(_) => {
-                return Self::from_early_bound_and_free_regions(tcx, region);
-            }
-            ty::ReStatic => {
-                me.kind = "restatic";
-            }
-
-            ty::RePlaceholder(_) => return None,
-
-            ty::ReError(_) => return None,
-
-            // FIXME(#13998) RePlaceholder should probably print like
-            // ReFree rather than dumping Debug output on the user.
-            //
-            // We shouldn't really be having unification failures with ReVar
-            // and ReLateBound though.
-            ty::ReVar(_) | ty::ReLateBound(..) | ty::ReErased => {
-                me.kind = "revar";
-                me.arg = format!("{:?}", region);
-            }
-        };
-        Some(me)
-    }
-
-    fn from_early_bound_and_free_regions<'tcx>(
-        tcx: TyCtxt<'tcx>,
-        region: ty::Region<'tcx>,
-    ) -> Option<Self> {
-        let mut me = DescriptionCtx::default();
-        let scope = region.free_region_binding_scope(tcx).expect_local();
-        match *region {
+        let (span, kind, arg) = match *region {
             ty::ReEarlyBound(ref br) => {
-                let mut sp = tcx.def_span(scope);
-                if let Some(param) =
+                let scope = region.free_region_binding_scope(tcx).expect_local();
+                let span = if let Some(param) =
                     tcx.hir().get_generics(scope).and_then(|generics| generics.get_named(br.name))
                 {
-                    sp = param.span;
-                }
-                if br.has_name() {
-                    me.kind = "as_defined";
-                    me.arg = br.name.to_string();
+                    param.span
                 } else {
-                    me.kind = "as_defined_anon";
+                    tcx.def_span(scope)
                 };
-                me.span = Some(sp)
+                if br.has_name() {
+                    (Some(span), "as_defined", br.name.to_string())
+                } else {
+                    (Some(span), "as_defined_anon", String::new())
+                }
             }
             ty::ReFree(ref fr) => {
                 if !fr.bound_region.is_named()
                     && let Some((ty, _)) = find_anon_type(tcx, region, &fr.bound_region)
                 {
-                    me.kind = "defined_here";
-                    me.span = Some(ty.span);
+                    (Some(ty.span), "defined_here", String::new())
                 } else {
+                    let scope = region.free_region_binding_scope(tcx).expect_local();
                     match fr.bound_region {
                         ty::BoundRegionKind::BrNamed(_, name) => {
-                            let mut sp = tcx.def_span(scope);
-                            if let Some(param) =
-                                tcx.hir().get_generics(scope).and_then(|generics| generics.get_named(name))
+                            let span = if let Some(param) = tcx
+                                .hir()
+                                .get_generics(scope)
+                                .and_then(|generics| generics.get_named(name))
                             {
-                                sp = param.span;
-                            }
-                            if name == kw::UnderscoreLifetime {
-                                me.kind = "as_defined_anon";
+                                param.span
                             } else {
-                                me.kind = "as_defined";
-                                me.arg = name.to_string();
+                                tcx.def_span(scope)
                             };
-                            me.span = Some(sp);
+                            if name == kw::UnderscoreLifetime {
+                                (Some(span), "as_defined_anon", String::new())
+                            } else {
+                                (Some(span), "as_defined", name.to_string())
+                            }
                         }
                         ty::BrAnon(span) => {
-                            me.kind = "defined_here";
-                            me.span = match span {
+                            let span = match span {
                                 Some(_) => span,
                                 None => Some(tcx.def_span(scope)),
-                            }
-                        },
+                            };
+                            (span, "defined_here", String::new())
+                        }
                         _ => {
-                            me.kind = "defined_here_reg";
-                            me.arg = region.to_string();
-                            me.span = Some(tcx.def_span(scope));
-                        },
+                            (Some(tcx.def_span(scope)), "defined_here_reg", region.to_string())
+                        }
                     }
                 }
             }
-            _ => bug!(),
-        }
-        Some(me)
-    }
 
-    fn add_to(self, diag: &mut rustc_errors::Diagnostic) {
-        diag.set_arg("desc_kind", self.kind);
-        diag.set_arg("desc_arg", self.arg);
-        diag.set_arg("desc_num_arg", self.num_arg);
+            ty::ReStatic => (alt_span, "restatic", String::new()),
+
+            ty::RePlaceholder(_) | ty::ReError(_) => return None,
+
+            // FIXME(#13998) RePlaceholder should probably print like
+            // ReFree rather than dumping Debug output on the user.
+            //
+            // We shouldn't really be having unification failures with ReVar
+            // and ReLateBound though.
+            ty::ReVar(_) | ty::ReLateBound(..) | ty::ReErased => {
+                (alt_span, "revar", format!("{:?}", region))
+            }
+        };
+        Some(DescriptionCtx { span, kind, arg })
     }
 }
 
@@ -198,10 +168,11 @@ impl AddToDiagnostic for RegionExplanation<'_> {
     {
         diag.set_arg("pref_kind", self.prefix);
         diag.set_arg("suff_kind", self.suffix);
-        let desc_span = self.desc.span;
-        self.desc.add_to(diag);
+        diag.set_arg("desc_kind", self.desc.kind);
+        diag.set_arg("desc_arg", self.desc.arg);
+
         let msg = f(diag, fluent::infer_region_explanation.into());
-        if let Some(span) = desc_span {
+        if let Some(span) = self.desc.span {
             diag.span_note(span, msg);
         } else {
             diag.note(msg);

compiler/rustc_infer/src/infer/error_reporting/mod.rs

@@ -184,84 +184,74 @@ fn msg_span_from_named_region<'tcx>(
     region: ty::Region<'tcx>,
     alt_span: Option<Span>,
 ) -> (String, Option<Span>) {
-    match *region {
-        ty::ReEarlyBound(_) | ty::ReFree(_) => {
-            let (msg, span) = msg_span_from_early_bound_and_free_regions(tcx, region);
-            (msg, Some(span))
-        }
-        ty::ReStatic => ("the static lifetime".to_owned(), alt_span),
-        ty::RePlaceholder(ty::PlaceholderRegion {
-            bound: ty::BoundRegion { kind: ty::BoundRegionKind::BrNamed(def_id, name), .. },
-            ..
-        }) => (format!("the lifetime `{name}` as defined here"), Some(tcx.def_span(def_id))),
-        ty::RePlaceholder(ty::PlaceholderRegion {
-            bound: ty::BoundRegion { kind: ty::BoundRegionKind::BrAnon(Some(span)), .. },
-            ..
-        }) => (format!("the anonymous lifetime defined here"), Some(span)),
-        ty::RePlaceholder(ty::PlaceholderRegion {
-            bound: ty::BoundRegion { kind: ty::BoundRegionKind::BrAnon(None), .. },
-            ..
-        }) => (format!("an anonymous lifetime"), None),
-        _ => bug!("{:?}", region),
-    }
-}
-
-fn msg_span_from_early_bound_and_free_regions<'tcx>(
-    tcx: TyCtxt<'tcx>,
-    region: ty::Region<'tcx>,
-) -> (String, Span) {
-    let scope = region.free_region_binding_scope(tcx).expect_local();
     match *region {
         ty::ReEarlyBound(ref br) => {
-            let mut sp = tcx.def_span(scope);
-            if let Some(param) =
+            let scope = region.free_region_binding_scope(tcx).expect_local();
+            let span = if let Some(param) =
                 tcx.hir().get_generics(scope).and_then(|generics| generics.get_named(br.name))
             {
-                sp = param.span;
-            }
+                param.span
+            } else {
+                tcx.def_span(scope)
+            };
             let text = if br.has_name() {
                 format!("the lifetime `{}` as defined here", br.name)
             } else {
                 "the anonymous lifetime as defined here".to_string()
             };
-            (text, sp)
+            (text, Some(span))
         }
         ty::ReFree(ref fr) => {
             if !fr.bound_region.is_named()
                 && let Some((ty, _)) = find_anon_type(tcx, region, &fr.bound_region)
             {
-                ("the anonymous lifetime defined here".to_string(), ty.span)
+                ("the anonymous lifetime defined here".to_string(), Some(ty.span))
             } else {
+                let scope = region.free_region_binding_scope(tcx).expect_local();
                 match fr.bound_region {
                     ty::BoundRegionKind::BrNamed(_, name) => {
-                        let mut sp = tcx.def_span(scope);
-                        if let Some(param) =
+                        let span = if let Some(param) =
                             tcx.hir().get_generics(scope).and_then(|generics| generics.get_named(name))
                         {
-                            sp = param.span;
-                        }
+                            param.span
+                        } else {
+                            tcx.def_span(scope)
+                        };
                         let text = if name == kw::UnderscoreLifetime {
                             "the anonymous lifetime as defined here".to_string()
                         } else {
                             format!("the lifetime `{}` as defined here", name)
                         };
-                        (text, sp)
+                        (text, Some(span))
                     }
                     ty::BrAnon(span) => (
                         "the anonymous lifetime as defined here".to_string(),
-                        match span {
+                        Some(match span {
                             Some(span) => span,
                             None => tcx.def_span(scope)
-                        }
+                        })
                     ),
                     _ => (
                         format!("the lifetime `{}` as defined here", region),
-                        tcx.def_span(scope),
+                        Some(tcx.def_span(scope)),
                     ),
                 }
             }
         }
-        _ => bug!(),
+        ty::ReStatic => ("the static lifetime".to_owned(), alt_span),
+        ty::RePlaceholder(ty::PlaceholderRegion {
+            bound: ty::BoundRegion { kind: ty::BoundRegionKind::BrNamed(def_id, name), .. },
+            ..
+        }) => (format!("the lifetime `{name}` as defined here"), Some(tcx.def_span(def_id))),
+        ty::RePlaceholder(ty::PlaceholderRegion {
+            bound: ty::BoundRegion { kind: ty::BoundRegionKind::BrAnon(Some(span)), .. },
+            ..
+        }) => (format!("the anonymous lifetime defined here"), Some(span)),
+        ty::RePlaceholder(ty::PlaceholderRegion {
+            bound: ty::BoundRegion { kind: ty::BoundRegionKind::BrAnon(None), .. },
+            ..
+        }) => (format!("an anonymous lifetime"), None),
+        _ => bug!("{:?}", region),
     }
 }